1. Technical Field
The present invention relates generally to the fabrication of semiconductor integrated circuit packages, and more specifically to packages with leadframes for passive devices.
2. Background Art
Digital products, such as cell phones and wrist watches have become aspects of everyday life. The core of these digital electronic products are integrated circuit die which continue to be made smaller and more reliable while increasing performance and speed.
An integrated circuit is typically packaged in a tiny box-type structure usually on the order of a few millimeters per side. The integrated circuit package generally has cylindrical terminals formed through a passivation layer of the integrated circuit die to square or rectangular contacts near its edges for directly bonding the integrated circuit die to a foil-type leadframe that is usually less than 0.5 mm in thickness. The integrated circuit packages are generally wire bonded or ball bonded to the foil-type leadframe. A body of a hardened, insulative encapsulant material then covers the integrated circuit die and the leadframe.
A series of problems related to the integrated circuit package and the leadframe becomes worse as the size of both decrease. Negative electrical effects such as electromagnetic interference, or undesirable coupling between leads in the leadframe, result in slowdown of electrical signals, cross-talk, or other problems.
To overcome these problems, passive components have been placed on the leadframe between the leads to eliminate negative electrical effects. These passive devices include capacitors, resistors, and inductors.
With the pressing demand on integrated circuit die to have higher density, higher integrity, compact size, and multiple functions, passive devices have also become smaller and lighter. As a result, they can be integrated into an integrated circuit package using surface mount technology (SMT). However, this has created its own set of problems with many different types of defects.
Keeping in mind that a passive device may be the size of a grain of sand, problems such as misalignment, bridging, drawbridging/tombstoning, or missing passive devices may occur. In bridging, the solder used to attach the passive devices may bridge or short-circuit adjacent passive devices. Misalignment means that the passive devices may only touch the solder connections so as to provide high resistance, or may actually not contact the solder connections required so as to produce an open circuit. Drawbridging/tombstoning occurs when the surface tension of solder lifts the passive device off the leadframe and results in an open circuit. A missing passive device can occur because the devices are extremely small and may be easily dislodged.
Prior developments have not taught or suggested any solutions, and, thus, solutions to these problems have long eluded those skilled in the art.